Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that there is a problem with the little heater in cylinder 9 of the engine. This heater helps the engine start when it's cold.
The engine control module (ECM) has detected an issue with the electrical circuit for the glow plug in cylinder 9. This could be due to an open circuit or a faulty glow plug.
The P0679 code indicates that the ECM has detected an open circuit or a malfunction in the glow plug circuit for cylinder 9. Glow plugs are used in diesel engines to heat the air in the cylinders to ensure proper combustion during cold starts.
• Difficulty starting the engine, especially in cold weather
• Engine runs rough during startup
• Check Engine Light is illuminated
• Faulty glow plug in cylinder 9
• Open or shorted glow plug circuit wiring
• Faulty glow plug control module
Glow Plug: A device used in diesel engines to heat the air in the cylinders for better combustion.
ECM: Engine Control Module, the computer that controls engine functions.
• Use an OBD-II scanner to confirm the code
• Inspect the glow plug and its wiring for damage
• Test the glow plug with a multimeter for resistance
• Replace the faulty glow plug
• Repair or replace damaged wiring in the glow plug circuit
• Replace the glow plug control module if necessary
• OBD-II scanner
• Multimeter
• Socket set
$100 - $300
Moderate
• Ford F-250
• Chevrolet Silverado
• Dodge Ram
• Regularly inspect glow plug connections
• Perform routine engine maintenance
• Use high-quality fuel
Engine Performance
• Have the vehicle diagnosed by a professional if unsure
• Avoid driving in extremely cold conditions until fixed
Glow plugs may be covered under the vehicle's powertrain warranty. Check with the manufacturer.
Glow plug circuit issues are common in older diesel engines, especially in cold climates.
Moderate – This issue can cause starting problems, especially in cold weather, but is not immediately dangerous.
Driving with a faulty glow plug can lead to increased emissions and potential engine damage.
• Engine off and cool
• Battery fully charged
Glow plugs are located in the cylinder head, near the fuel injectors.
Q: Can I drive with a P0679 code?
A: It's possible to drive with this code, but you may experience starting issues, especially in cold weather.
Q: How do I know if a glow plug is bad?
A: A bad glow plug can cause hard starting, rough idling, and increased smoke from the exhaust.
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